Acrylic fiber

ABSTRACT

ARCYLIC FIBER HAVING AN IMPROVED ANTIFLAMING PERFORMANCE AND COMPRISING A COPOLYMER OF MORE THAN 55 WT. PERCENT ACRYLONITRILE, 5-25 WT. PERCENT VINYLIDENE CHLORIDE. 4-25 WT. PERCENT MERTHACRYLONITRILE AND 3-14 WT. PERCENT ACRYLAMIDE AND/OR METHACRYLAMIDE.

United States Patent C 3,651,013 ACRYLIC FIBER Toshio Ohfuka, Yasushi Ichikawa, and Yoshiharu Sugaya, Shizuoka-ken, Japan, assignors to Asahi Kasei Kogyo Kabushiki Kaisha, Osaka, Japan No Drawing. Filed June 16, 1969, Ser. No. 833,728 Claims priority, application Japan, June 14, 1968, 43/ 40,582 Int. Cl. C08f 15/40 US. Cl. 26049 6 Claims ABSTRACT OF THE DISCLOSURE Acrylic fiber having an improved antifiaming performance and comprising a copolymer of more than 55 wt. percent acrylonitrile, -25 wt. percent vinylidene chloride, 4-25 Wt. percent methacrylonitrile and 3-14 wt. percent acrylamide and/or methacrylamide.

This invention relates to improved acrylic fiber containing as its main constituents acrylonitrile, vinylidene chloride, methacrylonitrile and acrylamide and/or methacrylamide.

Acrylic fibers made of acrylic polymer containing more than 85% of acrylonitrile are characterized by a sharp and durable dyeing property, in addition to a superior heat shrinkage performance highly suitable for the manufacture of bulky yarn.

Efforts have been made to provide antiflaming performance in acrylic fibers. Thus, it has already been proposed to provide as the antifiaming agent, for instance, an organic halogen compound or a halogen-containing organophosphorous compound in acrylic fibers. In this case, however, the antifiaming agent must be applied in a substantial quantity for attaining a satisfying antifiaming effect, resulting frequently in considerable adverse effects upon the physical properties, hand feeding, as well as the chemical nature such as dyeing performance of the fibers. In addition, it has frequently been encountered that the antiflaming agent as above specified is liable to scale oif in the course of conventional after-treatments of the fibers such as dyeing, scouring or the like steps, and thus the antiflaming properties given by these additives cannot be relied upon.

As an alternate measure, it has been proposed to copolymerize a certain halogen-containing vinyl monomer such as vinyl chloride or vinylidene chloride with an acrylic component as the main constituent of the fibers. In this case, the halogen-containing vinyl monomer must be used in substantial quantity, such as as high as 50% of the total quantity of the fiber-forming substance. If vinyl chloride is copolymerized at nearly a fifty-to-fifty rate with an acrylic compound, the product will be a representative kind of modacryl fiber which is substantially different from acrylic fibers and the resulting fiber has a lack of favorable characteristics.

Among the fiber characteristics, dyeing performance and heat shrinkage percentage are of most importance. As an example, when acrylonitrile and vinylidene chloride are copolymerized substantially in a fifty-to-fifty ratio, the fibers could not be sharply and durably dyed. In this case, even when a certain monomer such as sodium allyl sulfonate, sodium methallyl sulfonates or sodium styrene sulfonate which have an acid radical capable of acting as a dyesite for basic dyes, is copolymerized with the acrylic fiber component, it does not provide a satisfactory dyeing property, when exclusively relying upon the above mentioned measure. If, in order to avoid this drawback, monomer .as methyl acrylate, methyl methacrylate, vinyl acetate or the like is employed as a copolymerizing compo- 3,65Lfil3 Patented Mar. 21, 1972 nent, other drawbacks such as excessive heat shrinkage property, and disadvantageous glueing tendency during wet heat treatment will frequently be invited. The term glueing used herein indicates the tendency of the fibers to stick together to a larger or lesser degree which is especially disadvantageous in the course of the spinning stage of the fibers. In this respect, it should be noted that even only slightly glued fibers will give rise to forming disadvantageous slubs, neps, and the like, resulting in inferior quality products. The glueing property of the fibers depends largely upon the heat resistance property and thus the thermal shrinkability of the fibers, but not in an exclusive sense. Although the true and correct mechanism of the glueing is not known to us, it is supposed that the mutual sticking property and the surface conditions of the fibers which are naturally affected by the occasional kinds of the employed copolymer components have a substantial effect on the glueing. In addition, a high thermal shrinkability will disadvantageously and considerably afl ect the dimensional stability, especially in the case of ironing, the acrylic fibrous products.

'It is therefore the main object of the present invention to provide anti-flaming acrylic fibers having substantially none of the aforementioned conventional drawbacks.

These and further objects, features and advantages will become more apparent as the description proceeds.

In order to satisfy these objects, we have carried out a series of profound experiments upon various and different combinations of a large number of copolymerizable monomers with acrylonitrile, and found that when the fiber is manufactured from a copolymer comprising over 55% acrylonitrile, 5-25% vinylidene chloride, 4-25% methacrylonitrile and 3l4% acrylamide and/or methacrylamide, and preferably 0.l2% of an alkenyl monomer having at least one acidic radical, satisfactory antiflaming, dyeing, heat shrinking and antiglueing properties results. In the above formulation, percentages are all given by weight as is the case throughout the remainder of the present specification.

\According to our further experiments, it has been surprisingly found that the fiber thus prepared contains a large amount of copolymer components other than acrylonitrile, it represents superior physical properties comparative to acrylic fibers, and has a beautiful and brilliant color developing performance upon being dyed. One of ordinary skill in the art would not think that a fiber containing below percent acrylonitrile would provide desirous physical properties comparative to acrylic fibers, yet having a substantially improved antifiaming performance.

The fiber according to this invention includes about 5- 25% of vinylidene chloride to provide a satisfactory degree of antiflaming performance to the fiber. When the content of vinylidene chloride should be below about 5%, the desired antiflaming performance will become inferior. With a content of vinylidene chloride over 25%, the fiber will be liable to lose its transparency when subjected to a boiling treatment. In addition, the fiber, when dyed, does not provide a sharp and brilliant color tone. Still further, it will provide generally modacryl fiber-like characteristics which are not desirous in the case of this invention.

The addition of other copolymerizable components, more specifically methacrylonitrile and acrylamide and/ or methacrylamide according to the above specified formulation, will contribute to the realization of a substantial degree of improved antiflaming performance with substantially reduced glueing tendency. When employing other combination of copolymer constituents, even the adding quantity of vinylidene chloride added is within the above specified numerical range, the fiber will substantially lose the favorable characteristics of acrylic fibers and, in addition, the desired antiflaming performance of the fiber will become disadvantageously and substantially inferior. When other comonomers such as methyl acrylate or vinyl acetate are used in place of methacrylonitrile, the fiber shows a considerably increased thermal shrinkability and a substantial degree of the disadvantageous glueing tendency, as noted in the following Table 1. When methyl acrylate was used in place of acrylamide, the desirous antifiaming performance becomes considerable, as will be clear from the following Table 2.

4 than 4 wt. percent, the desired effect will be less than that which is expected and thus the shrinkage, dyeing and antiflaming characteristics of the manufactrued fibers become unbalanced.

By the use of acrylamide and/or methacrylamide which is/are copolymerized together with methacrylonitrile and within a specified range of 33-14%, the hydrophilic and hydrophobic properties of the fiber are interadjusted properly, and at the same time not only the dyeing per- TABLE 1 Shrinkage Percent of-- percentage upon wet Meth- Vinylheat Acryloacrylo- Methyl Vinylidene Acryltreatment nitrile nitrile acrylate acetate chloride amide at 120 0. Remarks 66.1 15.5 10.5 22.3 Non-glueing. 66.9 15.2 10.6 40.0 Rough feeling caused by giueing. 66.9 7.5 15.4 10.2 39.4 D0.

TABLE 2 Percent of- Meth- Vinyl- Acryloacryioidene Vinyl Methyl Acrylnitriie nitrile chloride acetate acrylate amide Fire properties 66.1 7. 9 15.5 10.5 High degree of antiiiaming performance. 66.4 7. 5 15.4 10. 7 Only Small degree of antifiarning performance. 67.4 7.0 15.1 10.5 D0.

From the foregoing Tables 1 and 2, it will be clear that methyl acrylate and vinyl acetate show substantially different behavior in the desired effects from those of methacrylonitrile and acrylamide.

The use of methacrylonitrile as one of the copolymerizable monomers together with vinylidene chloride for the fulfilment of the objects of the invention and in combination with acrylamide or methacrylamide provides a fiber having superior and desirous effects without inviting the disadvantageous glueing tendency, even if the quantity used amounts to a considerable value as specified hereinbefore. It has been further found that the use of methacrylonitrile as a copolymer constituent will contribute toward improving the heat stretching performance of the fiber in the presence of a concentrated aqueous nitric acid solution from the copolymerized substance. The improvement of heat stretching performance obtained, for instance, in the above mentioned way will result in various improved fiber characteristics. In addition, it should be noted that the fibers having superior heat stretching properties are capable of providing the least possible breakage and thus present the least possible trouble during fiber drafting where other fibers are more liable to wrap around drafting rollers. The substantial lack of the disadvantageous formation of fiber breakage will not only improve the manufacturing efficiency in an appreciable manner, but also provide tows and staples of rather superior quality.

On the contrary, when any other comonomer such as methyl acrylate, methyl methacrylate, vinyl acetate or the like is used in place of methacrylonitrile, even in combination with vinylidene chloride, the aforementioned kind of improvement in the heat stretchability of the fibers cannot be attained, and in most cases the stretchability becomes worse. Therefore, it can be positively concluded that the aforementioned improvement in heat stretchability of fibers depends specifically and largely upon the presence of methacrylonitrile. If the amount of methacrylonitrile is greater than the chemical resistance of the fibers may become worse, and furthermore the polymer, which will be formed during polymerization, especially in the case of aqueous suspension polymerization, is frequently emulsified, thereby inviting diificulty in filtration and inconvenience in handling. On the contrary, when the quantity of methacrylonitrile is smaller formance thereof is improved, but also the transparency of the synthesized fiber becomes stable. It should be noted that the present component serves to prevent the otherwise frequenly invited fibrillation of the fiber. On the other hand, a remarkable advantage of the use of this copolymer constituent resides in the improvement of the anti-flaming property, especially non-inflammability, of the fiber. This feature is naturally most advantageous for the attainment of the desirous effect of the invention.

If, however, the quantity-of acrylamide and/ or methacrylamide present should exceed a certain preferred limit, the thermal shrinkability of the fiber formed will become excessively larger than desired and the dimensional stability of the produced fiber will become worse. Especially, when the quantity exceeds about 15%, the disadvantageous glueing tendency which occurs during wet heat treatment of the fibers will become excessive, which must naturally be avoided. Under such conditions, especially when the copolymerization is performed in an aqueous medium, the number of hydrophilic groups will be excessively numerous, thus the viscosity of the slurry will become substantially higher than desired. On the contrary, when the number of hydrophilic groups is smaller than desired, the antiflaming property will be reduced below the desired value so that the addition of these constituent comonomers may amount to 3% or higher. In the prior art, various N-substituted acrylamides are known, but these substances have almost no effect in the above sense in sharp contrast to these copolymer constituents, or more specifically, acrylamide and methacrylamide.

As already mentioned, all the copolymer constituents are copolymerized with acrylonitrile. In this case, however, with the smaller addition of acrylonitrile than above specified, the resulting properties of the fiber may be considerably different from those attainable homopolyacrylonitrile, and thus, the quantity of acrylonitrile should preferably be higher than about 55 wt. percent. The sum of methacrylonitrile and acrylamide and/ or methacrylamide must be more than 8 wt. percent, especially more than 10 wt. percent, for the realization of desirous antiflaming, dyeing and the like desirous properties. With an amount higher than 10 wt. percent, the thermal stretchability can be substantially improved. This feature will be highly predominant and advantageous for a spinning process TABLE 3 Percent of- Vinyl Meth- Heat Acrylcv idene acrylo- Acrylstretching nitrile chloride nitrile amide factor I 1 These values are maximum possible heat stretching factors which are obtainable with no breakage in the yarn stretching stage.

When methacrylonitrile and acrylonitrile and/or methacrylamide are employed in combination, the prepared fiber represents a kind of multiplying effect of several fiber characteristics, especially antiflaming, dyeing and the like performance which results could not be, however, realized, when these comonomers are separately polymerized.

The quantity of vinylidene chloride does not always have a linear relationship with the antiflaming property of the fiber, which varies, indeed, depending upon the kinds and contents of other copolymerizable monomers employed. The combination of methacrylonitrile with acrylamide and/or methacrylamide will substantially enhance the antifiaming effect of the manufactured fiber. The addition of methacrylonitrile will favorably affect the heat shrinkage behavior of the fiber and provides a kind of multiplying effect in reducing the glueing tendency of the fiber, as a matter of higher importance. On the other hand, the presence of methacrylonitrile will favorably affect upon the desirous realization of increased doses of valuable and effective acrylamide and/ or methacrylamide.

The copolymerization of vinylidene chloride, methacrylonitrile and/ or methacrylamide with acrylonitrile, and acrylamide in the ratios proposed by the present invention will result in a highly improved acrylic fiber. The effects specifically obtained according to the novel teaching of the present invention by specifying specific kinds and quantitiesof the comonomers employed are shown in Tables 4-7 to follow, and in terms of the valuable and substantial fiber characteristics.

The copolymerization of this invention may be performed by any one of the following conventional techniques:

emulsion polymerization; suspension or solution polymerization in aqueous medium or that containing organic solvent.

The copolymerization process may be either batch, semicontinuous or continuous.

As the polymerization catalyst, any catalytic substance which may be activated by thermal decomposition, such as azobisisobutyronitrile, benzoyl peroxide, lauroyl peroxide and/or the like. Redox catalysts, which consist of a combination of oxidant and reducing agent, such as a combination of a member selected from the first group of ammonium persulfate, potassium persulfate, hydrogen peroxide and salt of hydroxylamine sulfonic acid, and a member selected from the second group of sodium bisulfite and sulfur oxide, may also be employed. The combination of hydroxylamine sulfonic acid or its salt with sulfurous acid or bisulfite is proposed as being the most preferred polymerization catalyst for use with the present process. Supposing that the conventional catalyst is employed and it is intended to obtain the copolymer in a high yield of 8090%, the stretchability of the fiber prepared from the copolymer will become substantially inferior and thus only low grade fibers may be obtained.

Therefore, with use of conventional catalysts, the polymerization degree should be 60-70% at the highest. On the contrary, when the proposed combination of hydroxylamine sulfonic acid or its salt with sulfurous acid or bisulfite is used as the copolymerization catalyst and the polymerization reaction is proceeded with the addition of methacrylonitrile, the stretchability and the physical properties of the produced fiber will not decrease if the polymerization degree should be increased to -90%. It is a great advantage accrued from the present invention that the polymer having the above-mentioned superior characteristics should be manufactured at a high yield considering that the high yield is a highly important factor in the manufacture of the fiber on an industrial scale. Secondly, when a reducing sulfur compound such as stated above should be employed in the polymerization reaction, acid radicals are formed in the polymeric product.

Formation of these acid radicals in the produced p0- lymeric product is highly advantageous since these radicals serve as dyesites for cationic dyes during subsequent dyeing of the produced fiber and help develop durable and brilliant dyed colors on the fiber. If it is feared that these radicals formed in the polymer product through the reaction with the catalysts are insuflicient for the desirous dyeing operation, an alkenyl monomer having at least one acid radical and copolymerizable with the above-mew tioned monomers may be added. As these supplementary monomers, the monomers known heretofore as having such properties, such as allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid, methallyloxibenzene sulfonate and the corresponding salts thereof, may be em ployed. These monomers may be used in amounts ranging between 0- about 3 wt. percent and preferably between 0.1-2 wt. percent as the occasion may demand. Other monomers may be used in small amounts provided that they help enhance the facility in conducting the subsequent slurry operation.

As these monomers, such known monomers as methyl acrylate, methyl methacrylate, vinyl chloride, styrene, N-methacrylamide, acrylic acid, methacrylic acid and the like may be used singly or in combination. These monomers may be added in a total amount of up to 5 wt. percent and preferably less than 1%. As the polymer thus obtained is soluble in any solvent so far used with acrylic polymers, it may be dissolved in concentrated aqueous solution of nitric acid, concentrated solution of zinc chloride or rhodanate, dimethylformamide, dimethylacetamide or dimethylsulfoxide. The spinning solution thus obtained IS then spun in a known manner by a dry or wet spinning process, and subjected to the stretching and heat treatment steps so as to provide a synthetic filament product. The spinneret used for extrusion of the spinning solution may be of the known type with either circular or profiled cross section.

The following several preferred numerical examples will be given for a better understanding of the invention. In these examples, parts are given by weight, if not otherwise specified. Solution viscosities are given in 1 sp./c. as measured at 35 C. with a fixed copolymer concentration of 0.2 g./ ml. in dimethylformamide as solvent. Dyeing afiinity was determined by using a dyestuff Sevron Green B manufactured and sold by DuPont, USA in a ratio of 20 wt. percent based on the weight mass of the fibers to be tested. The fibers were boilingly padded with the dyestufi" in a padding bath, 1:80, for an hour, and then the absorbancy of the residual padding bath liquor was measured by means of a spectrometer manufactured and sold by Hitachi Limited, Hitachi, Japan.

The antiflaming test was conducted in the following manner: a piece of the produced fiber, 1 gram, was carded by means of a hand card, and manually rolled into a ball. The latter was then inserted into a town gas flame, 30 mm. long, emerging from a nozzle of 0.5 mm. inside diameter, so that one third of the total length of the flame will be effective on the fiber being tested. The flame was extinguished after a lapse of 10 seconds. The ignitability of the fiber being tested Was then graded according to whether the fiber was burning at that time and whether the fiber kept on burning after removal of the flame. The test fiber piece which was not burned out but was eX- tinguished halfway was graded as being low in antifiaming property and the latter property was classified as substantial, medium and least according to the duration of combustion.

EXAMPLE 1.

As the polymerization vessel, a flask of -lit. capacity fitted with an agitator, was used, and monomers (see Table 4), water, initiators and emulsifiers were charged gradually through an inlet into the flask, while the polymerized products were taken out correspondingly therefrom through an outlet, as the reaction proceeded. The copolymerization process was thus carried out in a continuous way.

1 part of monomers (see Table 4), was used to parts of water, and the combination of sodium hydroxylamine N-sulfonate and sodium bisulfite was employed as an initiator for polymerization reaction, which was carried at 50 C. for an interval of 7 hours. The polymer having the composition as shown in Table 4 was obtained at a yield of 80-90%.

The thus obtained copolymer was then dissolved in 75%-concentrated nitric acid solution, maintained at 5 C., so as to provide a spinning solution, which was then extruded by way of a conventional spinueret into a coagulating bath of 40% nitric acid solution maintained at 5 C. The extruded fiber was then allowed to solidify, washed with water, stretched to 6.5 times in boiling water, dried, and thermally treated for 10 minutes with 120 C. saturated steam. The properties of the obtained fiber, that is, the dyeing afiinity, antifiaming property, percentage of thermal shrinkage following the treatment with 120 8 EXAMPLE 2 The reaction vessel of Example 1 was used. 1 part of monomers (see Table 5) was used to 10 parts of water and the combination of sodium hydroxylamine N-sulfonate and sodium bisulfite was used as an initiator. The polymerization reaction was carried out at- C. for a reaction interval of 20 hours and the copolymer having the composition as shown in Table 5 was obtained. The obtained copolymer was then dissolved in dimethylformamide and the resultant spinning solution was extrudedly spun into a coagulating bath maintained at 40 C. and consisting of 55% dimethylformamide and water. The resultant fiber was then stretched to 5 times as it was washed in boiling water, and dried. The properties of the obtained fiber, that is, the dyeing afiinity, antifiaming property, percentage of thermal shrinkage following the treatment with 120 C. saturated steam, and glueing property, of the fiber are listed in Table 5.

EXAMPLE 3 A polymerization reaction vessel, l., fitted with an agitator was charged with 1 part of various monomers (see Table 6), 6 parts of water, an initiator and an emulsifying agent. As an initiator, the combination of ammonium persulfate and sodium salt of bisulfuric acid was employed. The reaction was carried out at 50 C. for a reaction interval of 5 hours, and the copolymer having the composition as shown in Table 6 was obtained.

The copolymer was dissolved in a 59% zinc chloride aqueous solution and the spinning solution thus obtained was spun extrudedly into a 40% zinc chloride aqueous solution. The resultant fiber was then washed with water containing ethylenediaminetetraacetic acid, stretched to 7 times in boiling water, dried, and thermally treated for 10 minutes with C., saturated steam. Table 6 shows the antifiaming and other properties of the obtained fiber.

TABLE 5 Percent of-- Percent of- Thermal Vinyl- Meth- Methyl- Desired shrink- Glueing Acryloidene Aerylacrylometh- Methyl antifiaming Dyeing age pertendency nitrlle chloride amide nltrile acrylate acrylate performance atfinity centage oi fibers 63.9 13.9 7.9 10.1 4.2 Substantlal 36 25 None. 69.1 9.8 5.1 13.7 2.3 do 34 24 D0.

C. saturated steam, and the glueing property, are listed in Table 4.

TABLE 4 Percent of Percent of- Sodium Desired Thermal Vinylmethantishrinkidene Aeryl- Meth- Methyl Methyl allyl flaming Dyeage Glueing Acrylzr chlo amide acrylomethacrysuliopering pertendency nitrile ride nitrile aerylate late nate i'ormance atfinity centage of fibers Inventive..- 57.9 23.4 13.3 0.5 Substantia1 40 24 None.

63.7 15.7 10.6 0.5 do 46 22 Do. 60. 9 10.5 4. 2 40 16 Do. 70.0 10.6 4. 0 37 15 Do. 60. 0 6. 1 1 9. 7 48 25 Do. 58. 7 23.1 12. 9 38 23 Do. 81.1 10.3 3.4 31 15 D0. 71. 6 17. 1 5. 8 42 18 D0.

Reference... 57. 8 23. B 13. 0 56 43 Substantial 73. 9 16. 1 Least 48 26 Do. 70. 4 10. 0 4. 2 SubstantiaL- 54 47 Do. 72.9 18. 9 Least 26 11 Do.

1 Methacrylarnide was used in place of acrylamide.

3 Dyeing afiinity was low and coloration insuflieient.

Percent of-- Percent 01- Sodium V meth- Thermal Vinyl- Meth- Methyl allyl 'Desired shrlnk- .Glueing. Acryloidene Acrylacrylometh- Methyl sulior antlflamlng Dyeing age pertendency nitrile chloride amide nitrile acrylate acrylate nate performance affinity centage oi fibers, Remarks 61.5 6.5 8.2 0.5 SubstantlaL I 47 23 None..-...'..

67.2 17.3 12.7 40 41 Substantial.

l Dyed yarns were very liable to lose color and color developing performance was poor.

1 Stretchability was poor.

EXAMPLE 4 The reaction vessel of Example 1 was employed. 1 part of various monomers (see Table 7) was used to 10 parts of water, and the combination of potassium hydroxylamine N-sulfonate and sodium bisulfite was used as an initiator. The polymerization was carried out at 60 C. for an interval of 3 hours, and the copolymer having the composition as shown in Table 7 was obtained.

The copolymer was then dissolved in 75% purified nitric acid solution, maintained at 5 C., so as to give a spinning solution, which was then extruded by way of a spinneret into a coagulating bath of a 30% nitric acid solution, maintained at C.

The resultant fiber was then allowed to coagulate, washed with water, stretched to 6 times in boiling water, dried, and heat treated for 10 minutes with 120 C. saturated steam. Table 7 below shows the properties of the thus obtained fiber, that is, the antiflaming property, the percentage of thermal shrinkage following the treatment with 120 C. saturated steam, the stretchability and glueing property of the fiber.

rene, N-methacrylamide, acrylic acid, methacrylic acid and mixtures thereof.

2. The acrylic fiber of claim 1 wherein the sum of the amount of methacrylonitrile and acrylamide or methacrylamide is at least 10 weight percent.

3. The acrylic fiber of claim 1 which contains from 0 to less than 1 weight percent of said monomer selected from the group consisting of methacrylate, methylmethacrylate, vinyl chloride, styrene, N-methacrylamide, acrylic acid, methacrylic acid and mixtures thereof.

4. An acrylic fiber having an improved anti-flaming property consisting essentially of a copolymer of more than weight percent acrylonitrile, from 5 to 25 weight percent vinylidene chloride, from 4 to 25 weight percent methacrylonitrile and from 3 to 14 weight percent of at least one member selected from the group consisting of acrylamide and methacrylamide, the sum of the amount of methacrylonitrile and acrylamide or methacrylamide being at least 8 Weight percent,

said acrylic fiber further containing from 0.1 to 2 weight percent of an alkenyl monomer selected from the group consisting of allyl sulfonic acid, methallyl TABLE 7 Percent of- Sodium Thermal Vinylmethshrinkidene Meth- Methyl allyl Desired age per Glueing Acrylochlo- Acrylacrylometh- Methyl Vinyl sulioantiflaming centage, Heat tendency nitrile ride amide nitrile acrylate acrylate acetate nate performance percent stretchability oi fibers Inventive... 78.3 10.1 5.7 5.4 0.5 Medium--- 14 Satisfactory None.

68. 2 10. 3 5. 5 16. do. 14 Predominant. Do. 60.4 9.8 5.7 23. 16 do Do. 75.3 10.3 5.4 6. 18 Satisfactory Do. 74.0 10.2 10.4 5. 22 Predominan Do. 63.5 10.4 10.1 15. 22 do. Do. 55.7 9.5 10.5 24. 24 do- Do. 68.3 19.8 5.4 6. 15 Satisfactory. Do. 58.8 20.5 5.3 15. 14 Predominant--. Do. 57. 4 14. 1 5. 7 22. 18 Do. 63.9 20.3 10. 6 5. 24 Do. 55.8 17.3 10.7 16. 26 do Do. 55.6 9.7 10.1 24. 28 Satisfaotory.-..- Do. 62.5 19.7 7.1 9. 24 Predominant--- Do. 62.3 15.4 5.9 15. 0.1 .do 22 d0 Do. 79.1 12.1 3.9 4. 0.5 Medium... 13 Above medium- Do:

Reference-.- 68.7 12.6 4.3 7.0 6.3 0.3 Least.. 25 Unsatisiactory Substantial.

63.5 20.2 8.5 7.8 14 do Do.

1 The dyed yarns prepared from the reference fiber on the last line were liable to lose color.

What is claimed is:

1. An acrylic fiber having an improved anti-flamming property consisting essentially of a copolymer of more than 55 weight percent acrylonitrile, from 5 to 25 weight percent vinylidene chloride, from 4 to 25 weight percent methacrylonitrile, from 3 to 13 weight percent of at least one member selected from the group consisting of acrylamide and methacrylamide, the sum of the amount of methacrylonitrile and acrylamide or methacrylamide being at least 8 weight percent, and from 0 to less than 5 weight percent of a monomer selected from the group consisting of methylacrylate, methylmethacrylate, vinyl chloride, sty- JAMES A. SEIDLECK, Primary Examiner -S: M". LEVIN; Assistant'Examiner l References Cited 1 v UNITED STATES PATENTS 3,310,535

. r "85.5XA;855 3/1961 Mazzolini epaLann 260-78.5 7 V r 7 W 3,376,276 4/1968 St roh 26080.7 3

-Ufs.'c1 KR; 

